The most common and most likely answer to this crossword clue is the 5 letter word RAISE
I've seen this crossword clue in The Times
R
A
I
S
E
More clues leading to the result RAISE
- Put up and knock down, reportedly
- Bring up commendation, initially ignored
- Stand up outside a cairn
- Jack’s approval, quietly overlooked
- Lift light beams that can be picked up
- God is here ultimately to provide uplift
- Erect, beams to audience
- By the sound of it, completely destroy lift
- Bring up commendation, but not initially
- After initial cut, give positive response to extra money
Buddy explains!

The straight part
We know that "Jack" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jack = raise.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does RAISE mean?
RAISE noun- An increase in wages or salary; a rise (UK).
- A shoulder exercise in which the arms are elevated against resistance.
- A shot in which the delivered stone bumps another stone forward.
- A bet that increases the previous bet.
- (physical) To cause to rise; to lift or elevate.
- To create, increase or develop.
- To establish contact with (e.g., by telephone or radio).
- To respond to a bet by increasing the amount required to continue in the hand.
- To exponentiate, to involute.
- (of a verb) To extract (a subject or other verb argument) out of an inner clause.
- (of a vowel) To produce a vowel with the tongue positioned closer to the roof of the mouth.
- To increase the nominal value of (a cheque, money order, etc.) by fraudulently changing the writing or printing in which the sum payable is specified.
- To throw (an exception).
- A cairn or pile of stones.